Upgrade Dotty to 3.0.0

[anatoliykmetyuk]

No description provided.

[dwijnand]

[error] ## Exception when compiling 566 sources to /home/travis/build/scala/scala/build/quick/classes/library
[error] scala.reflect.internal.Symbols$CyclicReference: illegal cyclic reference involving object Predef

🤔 How does updating dottyVersion break a bootstrapped library compile??

[SethTisue]

Maybe we need to clean up somewhere, after we've built the new reference compiler but before we start using it?

[lrytz]

If I remember correctly, I think #9628 (comment) was exactly the same failure. It could be a new non-deterministic issue in the compiler, but it could also be an issue with travis-workspaces?